There are many existing devices that are used to detect the optical quality of the eye or other optical systems, including: autorefractors/ophthalmic refractometers, aberrometers, etc. All of the existing devices work by using a light source to illuminate the eye. Many devices, including the vast majority of autorefractors, use an infrared light source, but visible light sources are also used. Anyone who has used a standard camera with a flash will know that light from the flash will reflect off of the retina during photography. This reflected light will make the pupil appear red in a photograph of a human eye or appear greenish in a photograph of many animals' eyes. The reflected light will also have a particular pattern that is dependent upon the eye's optical distortions. Many existing/previous autorefractors or aberrometers are based on this principle, i.e., shining a light into the eye and then detecting the pattern of the reflected light after it has been distorted by the eye. The devices vary in the configuration or type of light source or in how the reflected light is detected (single images, lenslet arrays, telescope combined with a lenslet array, etc.). However, in each of those cases, a light is shined into the eye and then the magnitude of the refractive error is determined, and this is often based on the intensity slope of the light (brighter at either the top or the bottom of the pupil) that is reflected off of the retina and back out of the eye.
Therefore, methods, apparatus and systems are desired that improve the detection of an optical quality of the eye or other optical system and that overcome challenges in the art, some of which are described above.